The present invention relates to a seal material which is suitably used in an apparatus where the seal section thereof is irradiated with infrared light such as in an apparatus using infrared light such as a heat source in a semi-conductor industry or the like, an apparatus where there is a secondary infrared light generation because of use at a high temperature of 600xc2x0 C. or higher, specifically to a highly durable seal material which has excellent heat resistance and chemical resistance along with a minimal rise in temperature when irradiated with infrared light.
The present invention relates to a process for manufacturing a white elastomer seal material.
Elastomers such as silicon rubber and nitrile rubber have heretofore been widely used as seal materials. In particular, because of their excellent heat resistance and chemical resistance, fluoroelastomers are used as seal materials in automobile, aircraft, space exploration devices, industrial machinery, semi-conductor manufacturing equipment, and the like. Perfluoroelastomers are suitably used as seal materials in semi-conductor manufacturing equipment, because they have particularly outstanding heat resistance and chemical resistance. Seal materials comprising fluoroelastomers or perfluoroelastomers compounded with metal oxides have also been developed for improved plasma resistance, including white seal materials. For example, WO-A-9719983 discloses perfluoroelastomer compositions which can be effectively used in the processing conditions found in dry process semiconductor manufacturing environments. These perfluoroelastomer compositions are substantially free of elemental carbon and contain selected metallic reinforcing fillers and titanium dioxide which provides a certain degree of whiteness to the cured articles resulting from the compositions.
However seal materials which are used under environments which may be irradiated with infrared light suffer from the likelihood of degradation due to a rise in the surface temperature of the seal material. None of the prior art materials used have yet been able to solve the problem of the seal material undergoing degradation under such environments.
Under such circumstances, an object of the present invention is to provide a highly durable seal material which has excellent heat resistance and chemical resistance along with a minimal rise in temperature when irradiated with infrared light.
Another object of the present invention is to provide a process for manufacturing a white elastomer seal material wherein the process has enhanced productivity.
Specifically, the invention is aimed at providing a high surface whiteness seal material and a process for manufacture thereof.
The present invention resides in the discovery that enhancing the whiteness of the seal material surface enables the rise in the surface temperature of the seal material to be suppressed when the material is irradiated with infrared light, and the inventors"" further continued intensive study has led to the finding that a seal material having a whiteness of at least 90 as expressed by a W (Lab) color expression system under the conditions of a 2xc2x0 field of view and a C-light source is accompanied by a minimal rise in temperature when irradiated with infrared light.
In the first aspect of the present invention, a white elastomer seal material is molded from a composition comprising a perfluoroelastomer and a white pigment in an amount at least 3% by weight based on the weight of the composition and having a surface with a whiteness of at least 90 as expressed by a W (Lab) color expression system under the conditions of a 2xc2x0 field of view and a C-light source.
In the second aspect of the present invention, a process for manufacturing a seal material having a surface with a whiteness greater than 75 as expressed by a W (Lab) color expression system under the conditions of a 2xc2x0 field of view and a C-light source comprises molding a seal material from a composition comprising a perfluoroelastomer and a white pigment in an amount of at least 1% by weight based on the weight of the composition and dipping the molded seal material in aqueous hydrogen peroxide solution for a time sufficient to increase the initial whiteness of the white elastomer seal material by at least 5 units.
In the third aspect of the present invention, a process for manufacturing a seal material having a surface with a whiteness greater than 75 as expressed by a W (Lab) color expression system under the conditions of a 2xc2x0 field of view and a C-light source comprises molding a seal material from a composition comprising a perfluoroelastomer and a white pigment in an amount of at least 1% by weight based on the weight of the composition and irradiating the molded seal material with ultraviolet light for a time sufficient to increase the initial whiteness of the white elastomer seal material by at least 5 units.
In the fourth aspect of the present invention, a process for manufacturing a seal material having a surface with a whiteness greater than 75 as expressed by a W (Lab) color expression system under the conditions of a 2xc2x0 field of view and a C-light source comprises molding a seal material from a composition comprising a perfluoroelastomer and a white pigment in an amount of at least 1% by weight based on the weight of the composition and exposing the molded seal material to ozone for a time sufficient to increase the initial whiteness of the white elastomer seal material by at least 5 units.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.